Move print op to the new gpu back-end.

theano/sandbox/gpuarray/opt.py

@@ -288,6 +288,22 @@ def local_gpua_specifyShape(node):
     return tensor.specify_shape(*inp)
 
 
+def gpu_print_wrapper(op, cnda):
+    op.old_op.global_fn(op.old_op, numpy.asarray(cnda))
+
+
+@register_opt()
+@op_lifter([tensor.printing.Print])
+def local_gpu_print_op(node):
+    x, = node.inputs
+    if x.owner and isinstance(x.owner.op, HostFromGpu):
+        gpu_x, = x.owner.inputs
+        new_op = node.op.__class__(global_fn=gpu_print_wrapper)
+        new_op.old_op = node.op
+        return new_op(gpu_x)
+    return False
+
+
 @register_opt()
 @op_lifter([tensor.Join])
 def local_gpua_join(node):

theano/sandbox/gpuarray/tests/test_opt.py

@@ -5,8 +5,9 @@ from theano import tensor
 from theano.tests import unittest_tools as utt
 import theano.sandbox.gpuarray
 from theano.sandbox.gpuarray.type import GpuArrayType
-from theano.sandbox.gpuarray.basic_ops import GpuAlloc, GpuReshape, gpu_alloc
-from theano.sandbox.gpuarray.elemwise import GpuCAReduceCuda
+from theano.sandbox.gpuarray.basic_ops import (
+    GpuAlloc, GpuReshape, gpu_alloc, gpu_from_host, host_from_gpu)
+from theano.sandbox.gpuarray.elemwise import GpuCAReduceCuda, GpuElemwise
 from theano.sandbox.gpuarray.tests.test_basic_ops import (
     rand_gpuarray, mode_with_gpu, mode_without_gpu
     )
@@ -116,3 +117,19 @@ class TestSpecifyShape(TestSpecifyShape):
     mode = mode_with_gpu
     input_type = GpuArrayType
     pass
+
+
+def test_print_op():
+    """ Test that print ops don't block gpu optimization"""
+    b = tensor.fmatrix()
+    f = theano.function([b], theano.printing.Print()(b) * 2,
+                        mode=mode_with_gpu)
+    theano.printing.debugprint(f)
+    #print f.maker.fgraph.toposort()
+#[GpuFromHost(<TensorType(float32, matrix)>), <theano.printing.Print object at 0x3581210>(GpuFromHost.0), GpuElemwise{mul}(CudaNdarray{[[ 2.]]}, <theano.printing.Print object at 0x3581210>.0), HostFromGpu(GpuElemwise{mul}.0)]
+    topo = f.maker.fgraph.toposort()
+    assert topo[0].op == gpu_from_host
+    assert isinstance(topo[1].op, theano.printing.Print)
+    assert isinstance(topo[2].op, GpuElemwise)
+    assert topo[3].op == host_from_gpu
+    f(numpy.random.random((5, 5)).astype('float32'))